1. Field of the Invention
The present invention relates, in general, to an optical pickup device and apparatus for recording and reproducing information on and from an optical recording medium, such as a compact disk or a digital versatile disk.
2. Description of the Related Art
Recently, with the development of information and communication technology, networks, such as the Internet, have been rapidly popularized, so that a, large quantity of information has been actively exchanged through the networks. In such conditions, a read-only optical disk, such as a Compact Disk-Recordable (CD-R), or a rewritable optical disk, such as CD-Rewritable (CD-RW), has been spotlighted as a recording medium. Recently, an optical disk having a large capacity, such as Digital Versatile Disk (DVD)-R, DVD-RW and DVD-Random Access Memory (RAM), has been used as an information recording medium, as the wavelength of a semiconductor laser, a laser light source, is shortened, the diameter of a focal spot of an objective lens with a high Numerical Aperture (NA) is decreased, and a thin substrate is employed.
The recording of information on a CD-R or the like is executed after converting write data obtained from a Personal Computer (PC), etc. into Eight to Fourteen Modulation (EFM) signals. In this case, a problem arises in that marks are poorly formed due to the heat accumulation and insufficient cooling speed of an optical disk attributable to the difference between the compositions of the dye recording layers of optical disks being used. Therefore, even though EFM signals are required to be recorded without change, required lands or spaces cannot be formed.
Therefore, there has been employed a scheme of determining a unique write parameter of each of optical disks being used (hereinafter referred to as a “write strategy”) with respect to a write waveform which is a reference, and then maintaining an excellent write quality. However, this scheme is disadvantageous in that the load of a developer is increased to determine unique write strategies for respective optical disks being used, differences arise in write strategies, set using skillfulness based on previous experiences, and consequently differences arise in write qualities.
Further, recently, as demands for the recording on an optical disk at a high density or at a high speed are further increased, the width of a write pulse becomes fine in response to the demands.
However, for example, if the fine write pulse is generated at a pickup drive of an optical disk system and then provided to a semiconductor laser in an optical pickup through a flexible cable or the like, a write pulse having an exact shape cannot be transmitted due to the influence of the resistance or capacitance of the flexible cable.
Further, in order to produce high quality write data, it is necessary to vary write conditions according to the unique properties of optical pickups, as well as the compositions of dye recording layers constituting each optical disk or write speeds. However, it is difficult to learn the unique properties of an optical pickup at a pickup drive and reflect the learned properties in a write strategy.
Therefore, there has been proposed a technology to vary a write strategy at a pickup drive in consideration of the diameter of the light spot of an optical pickup (for example, refer to Japanese Patent Laid-Open Publication No. 2002-183960) has been proposed, or a technology to vary a write strategy at a pickup drive in consideration of the surrounding temperature of the optical pickup (for example, refer to Japanese Patent Laid-Open Publication No. 2001-297437).
However, the above technologies are problematic in that it is difficult to optimize a write strategy without the help of the pickup drive, and the efforts of a developer of the pickup drive are not improved at all. Further, it is actually difficult for a drive manufacturer, which cannot learn the optical properties of respective optical pickups, to set write strategies, in which the unique properties of optical pickups are reflected, at the pickup drive, as described above.